Hydroxyaryl, alkoxyaryl and acyloxyaryl olefins are of considerable commercial interest. These compounds are useful, for example, as monomers for the preparation of vinyl polymers. These materials can be polymerized by cationic and radical polymerization techniques. In some cases, these compounds can also be polymerized by anionic polymerization techniques.
The resulting poly(hydroxystyrene) polymers are useful in a wide variety of applications, e.g., in photoresists, in epoxy resins, as metal coatings, and the like. It is clear, therefore, that economical methods for the production of these materials would be of great interest.
One method known in the art for the preparation of such materials is the palladium-catalyzed reaction of certain aryl halides with olefins (commonly referred to as the "Heck" reaction) to afford certain styrene derivatives. For example, R. F. Heck (Pure and Applied Chemistry, Volume 50, Pages 691-701 (1978)) discloses the reaction of certain aryl bromides and iodides with methyl acrylate and dimethyl fumarate to provide the corresponding cinnamic acid derivatives.
A common problem with the "Heck" reaction is the production of stilbene type by-products even when the most simple of olefins (i.e., ethylene) is employed. See, for example Plevyak and Heck in Journal of Organic Chemistry, Volume 43, Pages 2454-2456 (1978). One prior art means employed to improve product yields in the "Heck" reaction is the addition of certain phosphine ligands for the palladium catalyst. See, for example, Ziegler and Heck in Journal of Organic Chemistry, Volume 43, Pages 2941-2946 (1978). While the use of such ligands does provide for improved yields of the desired styrene-type products, such ligands are extremely expensive and, therefore, render such conversions relatively unattractive for commercial scale operation.
Solvents disclosed in the prior art as useful for the "Heck" reaction are typically highly polar, water-miscible solvents. Such materials render product recovery and recycle of catalyst materials extremely difficult. Consequently, the "Heck" reaction as known in the art suffers many limitations which render it undesirable to carry out the process on other than a laboratory scale.
Few examples exist in the literature of the "Heck" reaction being used for the production of 4-hydroxyaryl olefins or 4-acyloxyaryl olefins. Such examples as do exist suggest that only highly reactive olefins, e.g., styrene and methyl acrylate, are useful in such processes. Such disclosures suggest that less reactive olefins than styrene or methyl acrylate would not be suitable for use in the Heck reaction with such 4-substituted aryl halides.
There is, therefore, a need for a process of producing 4-substituted aryl olefins which employs inexpensive catalyst components, allows for easy product recovery and catalyst recycle, and is effective even with olefins of relatively low reactivity.